A variety of display station sets and other means exist for displaying at a called station the directory number of a calling station after the parties establish a talking condition between the stations. In one arrangement, while a called party is talking, the telephone switching system performs calling station directory number identification upon request of the called party. There are also some subscriber-owned systems in which the directory number of the calling station is transmitted to the called station by devices positioned at both of the stations. However, these devices are only functional after the call has assumed a talking condition.
In situations where the privacy of the called party is important, a number of arrangements are available. Many require the use of an additional communications link which is an inefficient use unless justified by other needs. Another arrangement transmits the directory number of the calling station to the called station between successive ringing signals. However, this arrangement displays only dialed information such as the directory number of a calling station and is not so practical for other than use in a private branch exchange.